Over the past few years, the development of new ionization techniques has permitted the expansion of mass spectrometry into new and exciting fields of research such as protein sequencing and structural analysis of very large chemically and thermally labile biological molecules. It appears now, however, that there are limitations in present mass analyzers which can consist of low transmission, restricted mass range and low resolution. The Wien mass spectrometer, with its capabilities of operating with high beam energy with high transmission and virtually no upper mass limit at a resolution of about 10,000 should offer a significant addition to the available methodology for mass analysis. Our initial object is to construct a Wien filter mass spectrometer, based on previous design experience, that will have the following capabilities: 1) mass resolution of 10,000; 2) mass range greater than 100,000 (the Wien filter essentially has no upper mass limit); 3) acceleration voltage range of 4,000 to 50,00 V; and 4) position sensitive electrooptically coupled ion detector to permit integration of a portion of the sample spectrum with 100% duty cycle. The instrument initially will be used with liquid SIMS and field desorption types of ion sources to produce ions from high mass (3,000-100,000 daltons) bioorganic samples. Calibration of the mass scale will be established using alkali metal halide salt ion clusters as mass markers. After preliminary testing and evaluation of the mass spectrometer, the instrument will then be applied to important problems in structural elucidation of a variety of high mass organic samples such as biopolymers, proteins, hormones, etc. Finally, we will evaluate the performance of the Wien analyzer to determine its overall effectiveness as a high mass analytical instrument and to propose further refinements in its design.